Along with the continuous evolution of a wireless communication technology and standard, a mobile packet service has achieved a great development, and data throughput of a single terminal is continuously improved. For example, a Long Term Evolution (LTE) system may support data transmission at a maximum downlink rate of 100 Mbps within a 20 M bandwidth. In a subsequent enhanced LTE network, a data transmission rate will be further increased and even may reach 1 Gbps.
An existing LTE user plane data protocol stack is shown in FIG. 1. Downlink data received from a core network through a General Packet Radio Service Tunneling Protocol for the User Plane (GTP-U) layer, after being unpacked, is processed by a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer and a Port Physical (PHY) layer for sending to User Equipment (UE); and sending of uplink data is exactly opposite to that of the downlink data. At present, a data transmission link between a network and UE is a one-to-one dedicated link, so that signal quality and adopted resource size of the link determine data transmission performance therebetween. User experiences of the UE may be reduced if a resource adopted by the link is limited or the signal quality of the link is relatively poor, which is a huge challenge a mobile operator is confronted with now. Although being expanded year by year, network capacity may still not catch up with increase of the number of user terminals and requirements of users on data services.
In order to meet an increase requirement of data services, an operator increases Low Power Nodes (LPNs) or called small cells or Pico eNBs for hotspot enhancement in a process of deploying a new-generation communication network (such as an LTE network). At present, many corporations and operators tend to adopt a dual connectivity offloading technology for solving the problem of non-uniformity of areal distribution of services. In the dual connectivity offloading technology, a terminal may keep connections with two or more than two network nodes at the same time (dual connectivity in the present disclosure is only a general term and the number of connected nodes is not limited). As shown in FIG. 2, a master node is called a Master eNB (MeNB) or a macro eNB, and other nodes are called Secondary eNBs (SeNBs) or Pico eNBs or LPNs, and are connected with the master node through Xn interfaces. For example, UE keeps connections with a macro cell and an LPN at the same time. A network side may regulate transmission data amounts of the UE on an MeNB and an SeNB in real time in case of unbalanced network load, and meanwhile, if the SeNB is changed due to movement of the UE or another factor, the connection with the other cell may still be kept, and such a change may not cause excessive signalling impact.
During specific data transmission, for how to distribute data originally on a connection to two connections, it is considered that there may currently be multiple offloading manners in the art, and an offloading manner based on which the main problem is solved in the present disclosure is shown in FIG. 3. When downlink data is transmitted, service data of bearer 2 on an MeNB at a sender is divided into two parts in a PDCP layer, is submitted to a local lower RLC layer and an RLC layer of an SeNB respectively, and is finally sent to a terminal.
According to a data transmission mechanism in an existing protocol, there exists information interaction among different protocol layers in a data transmission process of a sender. In order to ensure effective transmission, a PDCP layer may implement information interaction with an RLC layer. For example, in FIG. 4, a PDCP layer may interact with an RLC layer to ensure effective transmission. For example, for bearer data mapped to an RLC Acknowledge Mode (AM): (1) a PDCP layer in a bearer on an MeNB side irregularly notifies an RLC layer in a corresponding bearer on an SeNB side that it discards a user plane data packet; and (2) after successfully sending a data packet sent by a PDCP layer in a certain bearer at the MeNB side, the RLC layer in the bearer at the SeNB side may send feedback information to the PDCP layer to notify the PDCP layer of a sending condition of the data packet.
When a PDCP layer and an RLC layer are located in the same eNB, interaction between the PDCP layer and the RLC layer may be specifically implemented completely in equipment, while in a dual connectivity scenario, a PDCP layer at an MeNB side and an RLC layer at an SeNB side are located in different eNBs, so that interaction therebetween involves interaction between the two eNBs, and an entity (called a PDCP layer entity for short below) where the PDCP layer at the MeNB side is located may interact with an entity (called an RLC layer entity for short below) where the RLC layer at the SeNB side only through an Xn interface. Based on a present definition about an attribute of an Xn interface, a bandwidth of the Xn interface is limited, a PDCP layer and an RLC layer directly send information irregularly at present, which may easily cause unbalance of amounts of information sent every time, and for example, an excessive amount of information is sent sometimes, but a small amount of information is sent at other times. When an MeNB or an SeNB sends excessive information, the information is required to be queued for sending due to the fact that a bandwidth of an interface is insufficient, which may cause the problem of delay. In addition, excessive information may also cause the problems of disorder and packet loss during information transmission.